It is important that some products, for example certain types of pharmaceuticals or biotech products, are maintained within a specified temperature range, typically 2° to 8° C., to prevent the product from being damaged, or its shelf-life being reduced relative to the shelf-life stated on the product. The product may be a very high value medicine or the like, which will be worthless if its temperature is not correctly controlled. This may be problematic during shipment and use of an insulated shipper will often be necessary to make shipment practicable.
Passive insulated shippers comprise an insulated container comprising an insulated outer casing which is lined with, or houses, a number of cool blocks, cool trays, gel packs, cool bricks or similar, which for the purposes of the present specification are collectively referred to as cool packs. These may be cooled until a phase change occurs in the refrigerant in the cool packs, where the subsequent phase change back from a solid to a liquid acts to maintain the contents of the container at a constant temperature. Examples of materials which change state from a solid to a liquid to produce a cooling effect, are paraffin wax and water-based solutions.
Although reference above and below is made only to cool packs and the requirement to maintain a product at or below a certain temperature, those packs may also be used to maintain a product above a certain temperature, for example to stop a product freezing if it is being shipped in a cold climate. Thus, although for the purposes of this specification they will be referred to only as cool packs and only the case of keeping the product cool will be discussed, it will be appreciated that the invention is equally applicable to applications where it is desired to maintain the product above a desired temperature and the description and claims are to be interpreted so as not to preclude such an application.
The container may have an additional layer of insulation panels between the cool packs and an outer insulating layer of foam or a similar material to improve thermal efficiency, for example if the shipment is taking place in a hot climate or over extended period of time.
A passive shipper of the type described above therefore has a number of cool packs which have to be inserted before the shipper is used, in order to permit the cool packs to be cooled before use. It is desirable that the cool packs are standardised, to reduce the number of types of cool packs to assist in selection. It is also desirable that each cool pack can be positioned in one of several orientations, to assist in locating them correctly. It is also desirable that the cool packs be held in place only by the outer insulated walls of the container and possibly any intermediate layer of insulation panels. It is also desirable, especially in the case of disposable shippers which are not intended to be returned, that they are relatively inexpensive to manufacture.